Fort Jefferson Fort Jefferson occupies one of the seven islands in the Dry Tortugas National Park, Fla., and is at the end of the Florida Keys. The historic fort has sparkling ocean views, a former prison, and one of the largest brick structures in the Western Hemisphere. It's also one of the least visited National Parks in the United States.

Fort Jefferson Fort Jefferson occupies one of the seven islands in the Dry Tortugas National Park, Fla., and is at the end of the Florida Keys. The historic fort has sparkling ocean views, a former prison, and one of the largest brick structures in the Western Hemisphere. It's also one of the least visited National Parks in the United States. (Associated Press/J. Pat Carter)